The invention relates to a joining and attachment piece for corrugated tubes, with at least one hollow core space encompassed by a housing with an insertion opening for receiving one end of the tube and with an opposing through-passage, as well as at least one elastic element which is provided with cams for engaging the depressions on the cylinder surface of the corrugated tube and with an outer ring for locking the elastic element in a locked position.
Corrugated tubes are widely employed, in particular as protective tubing for cables, for example control cables. Various embodiments of joining and attachment pieces are known, by means of which corrugated tubes can be connected to one another or to housings. In U.S. Pat. No. 4,440,425 a solution of this type is for example described. In this solution the joining or attachment piece comprises a tubular housing with a hollow core space into which the end of a corrugated tube is slid. On the front end of the housing, incisions are provided through which tabs are cut out of the cylinder of the housing. These elements bear cams on their inside, which engage the depressions on the cylinder surface of the corrugated tube. When sliding the corrugated tube into the housing of the joining or attachment piece, the tabs can be widened outwardly, which permits sliding in the tube. To establish the connection between the joining or attachment piece and corrugated tube, at least one male fitting ring is disposed on the housing, which ring can be moved on the housing cylinder. A locking cam and a final stop are provided on the housing tabs, which serve to position the male fitting ring in the clamping position. Before the end of the tube is slid into place, the male fitting ring or the outer ring is located in a position behind the locking cam so that the housing tabs can spring open in the outward direction through their intrinsic elasticity or can be displaced by the inserted tube. As soon as the tube end in the joining or attachment piece has been brought into the desired position, the male fitting ring is slid over the locking cam and the housing tabs are pressed against the cylinder surface of the corrugated tube. The inner diameter of the male fitting ring is dimensioned so that a firm form-fitting connection results. The male fitting ring in this connection position is located between the locking cam and the final stop, both of which are implemented so that under normal operating conditions the ring is held firmly in this position.
Because of the housing tabs cut into the housing, the strength of the Joining and attachment piece described here is considerably reduced. Under heavy loads, fractures can occur at the end portions of the tabs or at other portions of the housing. As a consequence, the security of the connection is no longer ensured. In the event the connection between tube and attachment piece is established carelessly, there is also the danger that the male fitting ring is pushed over the tabs before the tube end has been slid sufficiently far into the attachment piece. In this case there is the danger that the tube end is not held properly and that it can be torn out of the connection. Since the male fitting ring, which forms the locking element for the tabs, is disposed on the outer cylinder surface of the joining or attachment piece, the danger also exists that it is unintentionally pushed from the locked position into the starting position. In this case the connection between tube end and attachment piece would be broken, which is undesirable. If the ring and the locking cam were to be implemented so as to be so strong that the unintentional detachment is practically avoided, the locked connection could no longer be broken without destroying the joining or attachment piece. This would make handling connections of this type difficult and expensive when they are to be disassembled or modified.
From DE-A-3 626 403 a further solution is known in which the elastic elements on the housing are not disposed on the front end in the form of free tabs but rather are integrated into the housing. This allows greater strength of the housing since the housing remains closed in the form of a ring at the front end. Locking the elastic elements here also takes place with the aid of an outer ring in the form of a male fitting sleeve. This male fitting sleeve also rests on the outer cylinder surface of the housing of the joining or attachment piece and is slid on this cylinder surface in the axial direction. In this case the danger also arises that the male fitting sleeve is unintentionally displaced and that through this displacement the connection between tube end and attachment piece is broken. If this is to be avoided, the connection must be formed so that it is no longer detachable. In the case of this suggestion for a solution the tube end can be clamped tightly in the joining or attachment piece before it has been slid entirely into the hollow core space. Accordingly, the danger of forming an unsatisfactory connection exists as well as the possibility that the tube end is torn out of the attachment piece.